The invention relates to a heat exchanger having lamella fins which are held at a distance from and parallel to each other by shaped collars on the lamella fins and which are penetrated by pipes running parallel to each other in passages through the collars, in each case the internal diameter of the passage matching the external diameter of the pipe and at least partially contacting the external periphery of the pipe.
In such a heat exchanger known from the German Offenlegungsschrift 2,123,722 the shaped collars of the lamellas are distributed in the lamella surface in order to guarantee the spacing of the lamellas from each other. This certainly produces a good degree of turbulence in the cooling air flowing through the heat exchanger, but it also gives rise to the corresponding resistance to a throughflow. However, such a resistance is undesirable, especially at the low speeds of travel of vehicles in urban traffic. If a firmer material is to be used for the lamella fins in order to increase the strength, then the rims of the shaped collars tend to rupture, because too high a demand is placed on the deformability of the material of higher strengths. Cracks in the lamella fins interfere with the heatflow, increase the resistance to throughflow, encourage corrosion and thereby reduce the useful life of the heat exchanger.
It is known from GB 2,047,399 to solder freepunched, bent tongues of lamella fins to the pipes of the heat exchangers. The heatflow is greatly hindered by the few relatively narrow bent tongues.